The present invention relates to a method for executing a water jet peening for giving an impact force to a surface of a structure member by a crushing pressure of a water jet and cavitation and improving the residual stress, or washing, or reforming the surface.
In Japanese Patent Laid-open No. Hei 7(1995)-328855, in a water jet peening method, to enhance effect of the water jet peening, it is disclosed to change the stand-off distance, injection pressure, or injection collision time. In Japanese Patent Laid-open No. Hei 6(1994)-047668, in a water jet peening apparatus, to enhance effect of the water jet peening, it is disclosed to detect an impact pulse when cavitation is generated, and to set the conditions of the distance between an injection nozzle and a execution object of the water jet peening and the injection pressure from the injection nozzle.